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Set up antivirus on Windows

We'll turn on Windows Defender, run a scan, and configure protection—or add exclusions for trusted apps.

How-to · Security basics
10–20 min
What you'll need
  • Windows 10 or 11
  • Admin access (for some settings)

At a glance

  • Windows Defender is built in—open Windows Security and confirm it is on.
  • Turn on Real-time protection and Cloud-delivered protection.
  • Run a full scan to check for existing threats.
  • Add exclusions only for trusted apps that Defender falsely flags.
Quick triage — pick your path

Get started

Choose the option that matches what you see. You can jump straight to that section.

Steps

Goal: Turn on and configure Windows Defender so your PC is protected.

  • Open Windows Security from Start or the system tray.
  • Good: Dashboard opens. Proceed to Real-time protection.

Real-time protection

Goal: Confirm Real-time protection and Cloud-delivered protection are on.

  • Virus & threat protection, Manage settings. Turn on Real-time protection and Cloud-delivered protection.
  • Good: Both are On. Proceed to Run a scan.

Run a scan

Goal: Check for existing threats.

  • Virus & threat protection, Scan options, Full scan, Scan now. Wait for the scan to finish. Remove or quarantine any threats found.
  • Good: No threats or threats cleaned. Proceed to Verification.

Exclusions

Goal: Add an exclusion only when Defender blocks a trusted app.

  • Virus & threat protection, Manage settings, Exclusions, Add an exclusion. Add the app folder or .exe.
  • Good: Exclusion added. Proceed to Verification.

Verification

  • Real-time protection is On in Windows Security.
  • Full scan completed with no threats (or threats removed).
  • Virus & threat protection updates are current.

When to get help

If Defender keeps flagging a program you trust, add an exclusion. If you suspect malware that Defender does not catch, run a second-opinion scan with Malwarebytes (free) or contact a technician. For Defender blocking an app, see Fix antivirus that blocks a program.

Reviewed by Blackbox Atlas

Frequently asked questions

Do I need to install antivirus on Windows?
Windows Defender is built in and sufficient for most users. Turn it on in Windows Security. Only install a third-party antivirus if you prefer it—do not run two real-time antivirus programs at once.
How do I run a virus scan on Windows?
Open Windows Security, Virus & threat protection, Scan options. Choose Full scan and click Scan now. The scan may take 30 minutes or more.
What if Defender blocks a program I trust?
Add an exclusion for the app. Go to Virus & threat protection, Manage settings, Exclusions, Add an exclusion. Choose the app folder or .exe. Only exclude apps you trust.

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